The invention is based on a priority application EP 04291797.1 which is hereby incorporated by reference.
The present invention relates to mobile communication systems, and more particularly, to a method for terminal-assisted interference control in mobile communication systems employing multiple sub-carriers, such as Orthogonal Frequency Division Multiplexing (OFDM) mobile communication systems.
In general, a mobile communication system supporting a wireless communication service comprises a radio access network communicating via an air interface with the user terminals. More particularly, the radio access network comprises a plurality of base stations controlled by a radio network controller (RNC), the base stations being in charge of communicating with the user terminals which are located inside their cell service area. As already well known in such cellular structures, generally the communication service provided to the user can substantially deteriorate due to neighbor cell interference or inter-cell interference.
In order to compensate the effects of inter-cell interference for user terminals located in defined cell regions and increase the quality of service received by the users in such regions, some interference control methods for an OFDM communication system are proposed in document “OFDM with interference control for improved HSDPA coverage”, R1-04-0572, Montreal Canada, 10-14 May 2004. In said document, it is proposed that e.g. when the terminal moves inside a service overlapping region near the cell border, said terminal measures the pilot signal from the interfering neighbor base stations in that region and signals to the mobile radio network information about the strength of reception from these base stations. The mobile network, based on the terminal information, tries to reserve for that terminal the same time-frequency group for communication in the serving base station and at least one of the other base stations serving in the overlapping region.
Such prior art solution however uses a time-frequency group reservation procedure by the mobile network for an undefined time based on a prediction of traffic load on the concerned cells. Such systems have the disadvantage that a number of time-frequency groups are reserved for terminals during an undefined time interval, the time in which the terminal remains in a service overlapping region near the cell border, even though the groups may not actually be used in certain time slots for data transmission, thus wasting overall system capacity resources. The prior art solution does not take also into account the rest of the terminals which are not located in that service overlapping region, for example, the ones that are close to the serving base station, and does not take into account the whole inter-cell interference influence for all terminals involved in the scheduling of the time-frequency groups in a multi-cell scheduling scenario.